The problem of uniformly applying a liquid across a relatively wide, continuously moving web is addressed in U.S. Pat. No. 4,165,211 granted on Aug. 21, 1979. Disclosed in that patent is an arrangement in which a liquid formable reaction mix is supplied from a source to an elongated reservoir through a plurality of nozzles spaced therealong. When the liquid reaches a predetermined level in the reservoir, it overflows onto either an inclined plate or curved blade causing a film of the foamable reaction mix to be deposited onto the moving web passing underneath the plate or blade. Since the reservoir's width substantially corresponds to the width of the web, a uniform coating of the liquid mix is applied to the latter whereby a subsequent reaction produces a uniform foam layer on the web.
While the apparatus just described may be used to uniformly apply to a web a liquid which eventually will become foam, the applicator is not suitable for uniformly depositing form on the web, a procedure which is employed for such purposes as dyeing carpet. Instead, known methods of applying foam to a web have taken diverse forms, such as those disclosed in U.S. Pat. Nos. 4,275,683, issued on June 30, 1981, and 4,297,860, which granted on Nov. 3, 1981. The latter patent also mentions that previously known foaming techniques generally utilized metering rolls and/or doctor blades for achieving uniform distribution of the foam on the web.
Only a brief consideration of prior art foam applicators is required to appreciate that they are limited to the application of foam to a web. However, the present invention is characterized by its ability to uniformly apply either liquids or foam to moving webs of substantial widths. Accordingly, the invention is particularly suited for use in the carpet industry to apply dyes to carpet either as foam or as a liquid. This, of course, provides a decided economical advantage since the same equipment can be used for either type of operation.